Abstract
C‐reactive protein (CRP) is an acute phase marker and a predictor of the risk of developing atherosclerotic complications. However, as a predictor of this risk, high sensitivity measurements are needed, and high sensitive CRP (hsCRP) assays have been developed. In this study, we experimentally compared two hsCRP assays, based on nephelometry and turbidimetry, both implemented on automated analyzers. Linearity, imprecision, turbidity interference, and results in the assay of 96 samples have been compared. Method comparison of the same two analytical systems in the assay of CRP was also performed on the basis of results in an interlaboratory external quality assessment scheme (EQAS). The two systems were found to perform substantially equally, both in hsCRP and in CRP measurement, but in the hsCRP assay the precision of nephelometry (CV% in the interval 3.0–5.8) was lower than that of turbidimetry (CV% in the interval 1.8–2.3). The classification of results by the two methods into three predefined relative risk classes gave 18% rate of discordance, in any case by one class only. The two methods proved reliable and comparable in the measurement of hsCRP, but precision should be improved. J. Clin. Lab. Anal. 18:280–284, 2004. © 2004 Wiley‐Liss, Inc.
Keywords: atherosclerosis, C‐reactive protein high‐sensitivity, immunoassay, nephelometry, turbidimetry
REFERENCES
- 1. Szalai AJ, Agrawai A, Greenhouch TJ, Volanakis E. C‐reactive protein: structural biology and host defenser function. Clin Chem Lab Med 1999;37:265–270. [DOI] [PubMed] [Google Scholar]
- 2. Thompson D, Milford‐War A, Whicher JT. The value of the acute protein measurements in clinical practice. Ann Clin Biochem 1992;29:123–131. [DOI] [PubMed] [Google Scholar]
- 3. Danesh J, Wheeler JG, Hirschfield GM, et al. C‐reactive protein and other circulating markers of inflammation in the prediction of coronary heart disease. N Engl J Med 2004;350:1387–1397. [DOI] [PubMed] [Google Scholar]
- 4. Pearson TA, Mensah GA, Alexander RW, et al. Markers of inflammation and cardiovascular disease. Application to clinical and public health practice. Circulation 2003;107:499–511. [DOI] [PubMed] [Google Scholar]
- 5. Roberts WL, Sedrick R, Moulton L, Spencer A, Rifai N. Evaluation of four automated high sensitivity C‐reactive protein methods: implications for clinical and epidemiological applications. Clin Chem 2000;46:461–468. [PubMed] [Google Scholar]
- 6. Roberts WL, Moulton L, Law TC, et al. Evaluation of nine automated high sensitivity C‐reactive protein methods: implications for clinical and epidemiological applications. Part 2. Clin Chem 2001;47:418–425. [PubMed] [Google Scholar]
- 7. Eda S, Kaufmann J, Molwitz M, Vorberg E. A new method of measuring C‐reactive protein, with a low limit of detection, suitable for risk assessment of coronary heart disease. Scand J Clin Lab Invest 1999;59 (suppl 230):32–35. [PubMed] [Google Scholar]
- 8. Rothkrantz‐Kos S, Bekers O, Gubbels A, et al. Evaluation of two new high‐sensitivity methods for C‐reactive protein. Ann Clin Biochem 2003;40:398–405. [DOI] [PubMed] [Google Scholar]
- 9. Rothkrantz‐Kos S, Schmitz MPJ, Bekers O, Menheere PCA, Van Dieijen‐Visser MP. High‐sensitivity C‐reactive protein methods examined. Clin Chem 2002;48:359–362. [PubMed] [Google Scholar]
- 10. Khuseyinova N, Imhof A, Trischler G, et al. Determination of C‐reactive protein: comparison of three high‐sensitivity immunoassays. Clin Chem 2003;49:1691–1695. [DOI] [PubMed] [Google Scholar]
- 11. De BK, Smith LG, Owen WE, Roberts WL. Performance characteristics of an automated high‐sensitivity C‐reactive protein assay on the dimension RXL analyzer. Clin Chim Acta 2002;323:151–155. [DOI] [PubMed] [Google Scholar]
- 12. Ridker PM. Clinical application of C‐reactive protein for cardiovascular disease detection and prevention. Circulation 2003;107:363–369. [DOI] [PubMed] [Google Scholar]
- 13. Macy EM, Hayes TE, Tracy RP. Variability in the measurement of C‐reactive protein in healthy subjects: implications for reference intervals and epidemiological applications. Clin Chem 1997;43:52–58. [PubMed] [Google Scholar]
- 14. Franzini C. Need for correct estimates of biological variation: the example of C‐reactive protein [letter]. Clin Chem Lab Med 1998:36;131–132. [DOI] [PubMed] [Google Scholar]
- 15. Ockene IS, Matthews CE, Rifai N, Ridker PM, Reed G, Stamek E. Variability and classification accuracy of serial high‐sensitivity C‐recative protein measurements in healthy adults. Clin Chem 2001;47:444–450. [PubMed] [Google Scholar]
- 16. Whicher JT, Ritchie RF, Myron Johnson A, et al. New international reference preparation for proteins in human serum (RPPHS). Clin Chem 1994;40:935–938. [PubMed] [Google Scholar]
- 17. Kimberly MM, Vesper HW, Caudill SP, et al. Standardization of immunoassays for measurement of high sensitivity C‐reactive protein. Phase I: evaluation of secondary reference materials. Clin Chem 2003;49:611–616. [DOI] [PubMed] [Google Scholar]